One of the goals of digital color management technology is to allow customers to unambiguously communicate their color reproduction requirements to print operators. In order to achieve this, digital color management systems require that a color space that is used to encode digital document files be communicated to the print operator. This is typically accomplished by tagging the digital document or individual elements within the document with an ICC color management profile. However, documents supplied to print operators as digital files are frequently not tagged with an ICC profile and, as a result, print operators are unsure as to how a document should appear when printed. In the absence of the required color management information, customer requirements can be difficult to determine. Some customers will communicate their requirements by supplying the print operator with an aim print or proof to be matched. If no proof is supplied, print operators will try to produce a print that their customer will find pleasing and acceptable. This is largely a matter of aesthetic judgment on the part of the print operator.
This lack of specific color management information requires digital press operators to guess at the correct color requirements. This is often done by testing various color management assumptions to determine which gives the most satisfactory results. These various color management assumptions can be tested by the choice of control parameter settings in the raster image processing (RIP) operation. The RIP operation translates document specifications in a page description language (PDL) such as Postscript and Adobe PDF into a set of color bitmap separations that are images of the document pages. It is an application that runs on a computer commonly called a Digital Front End (DFE) in the digital printing business. One of the more commonly used RIP control parameters is the choice of printer emulation. Other important control parameters might include rendering intents and GCR (gray component replacement) settings.
Regardless of whether the print operator is attempting to match a customer-supplied proof or simply produce a pleasing result, a range of different settings of the control parameters at the RIP will generally need to be tested before a successful outcome is achieved. Unfortunately, there is no simple or intuitive way for the print operator to determine the combination of settings that will produce the most desirable result. Accordingly, print operators will usually make a guess at what they think are the most likely RIP settings that will result in desirable color reproduction. They will then proceed to test many combinations of these settings until satisfactory results are obtained. This process can require a large number of single-print tests and is quite time consuming as each test must be manually set up and initiated on the DFE.
U.S. Pat. No. 6,803,921 discloses one approach to improving the aforementioned printing process. This patent document discloses a softcopy proofing system in which an image or document of unknown colorimetry can be soft proofed iteratively using a range of different source profiles, rendering intents and color adjustments. This disclosed procedure is similar to, but more application specific than, the time consuming, manual process described above as the current test methodology being used by pre-press operators, except it is performed using a softcopy proofing device rather than on the actual press. Furthermore, it only considers color management source profiles and rendering intents and does not apparently relate to the full range of control parameters available on the printer RIP. The approach disclosed in U.S. Pat. No. 6,803,921 does not apparently provide the capability to make direct side by side comparisons of the effects of changing various settings on actual prints. Color gamut mismatch between the softcopy proofing device and the actual press and the difference between the typical viewing environments for softcopy displays and actual prints further evidences the application specific nature of this method.